1. Field of the Invention
The present invention relates to an apparatus for fabricating a liquid crystal display device, and more particularly, to a rubbing apparatus having a turning buffer for fabricating a liquid crystal display device.
2. Discussion of the Related Art
A liquid crystal display device includes a thin film transistor array substrate, a color filter substrate bonded to the thin film transistor array substrate to have a uniform cell gap, and a liquid crystal layer inserted in the cell gap between the thin film transistor array substrate and the color filter substrate.
Pixels are arranged in a matrix form on the thin film transistor array substrate. A thin film transistor (TFT), a pixel electrode, and a capacitor are formed in a unit pixel. And, a common electrode, an RGB color filter, and a black matrix are patterned on the surface of the color filter substrate.
Meanwhile, alignment layers are formed on the surfaces of the thin film transistor array and the color filter substrates facing into each other. And, rubbing is carried out on the alignment layers to align liquid crystals in a predetermined direction. In this case, when an electric field is applied between the pixel electrode on each unit pixel of the thin film transistor array substrate and the common electrode on the entire surface of the color filter substrate, the liquid crystals are rotated by dielectric anisotropy to transmit or cut off light by each unit pixel for displaying a character or an image.
A method of fabricating a liquid crystal display device will be briefly explained as follows.
Thin film transistor array substrates are prepared on a first mother substrate, and color filter substrates are prepared on a second mother substrate.
As mentioned in the foregoing explanation, pixels are arranged in a matrix form on each of the thin film transistor array substrates. A thin film transistor, a pixel electrode, and a capacitor are formed in the unit pixel. A common electrode, a color filter, and a black matrix are patterned on each of the color filter substrates.
Subsequently, alignment layers are formed on each surface of the first and second mother substrates. Rubbing is then carried out on the alignment layers. In this case, a rubbing cloth is used to rub the surface of each of the alignment layers at an equal force and speed in order to align polymer chains on the surface of the corresponding alignment layer in a predetermined direction for aligning liquid crystals.
And, the first and second mother substrates are bonded to each other so that the alignment layers on the surfaces of the first and second mother substrates face into each other. In this case, spacers are inserted between the first and second mother substrates to provide a uniform cell gap between the bonded first and second mother substrates.
Thereafter, liquid crystal display panels formed on the bonded first and second mother substrates are cut individually to separate into a plurality of unit liquid crystal display panels.
FIG. 1 illustrates a schematic perspective view illustrating rubbing directions of alignment layers on first and second mother substrates according to a related art.
As shown in FIG. 1, a rubbing direction 12 of the alignment layer on the surface of a first mother substrate 10 lies from an upper left corner to a lower right corner of the first mother substrate 10, while a rubbing direction 22 of the alignment layer on the surface of a second mother substrate 20 lies from a lower left corner to an upper right corner of the second mother substrate 20.
FIG. 2 illustrates a schematic perspective view illustrating the rubbing directions 12 and 22 shown in FIG. 1 where the first and second mother substrates 10 and 20 are bonded to each other to have the alignment layers 11 and 21 facing into each other.
FIG. 3 illustrates a schematic perspective view carrying out rubbing on the alignment layer 11 on the surface of the first mother substrate 10 according to the related art.
As shown in FIG. 3, while the first mother substrate 10 moves in a direction in parallel with a longer side of the first mother substrate 10, a roller 14 covered with a rubbing cloth 13 is installed to be tilted at a predetermined angle θ with respect to the longer side of the first mother substrate 10 and is rubbed on the alignment layer 11 to carry out a rubbing process.
Hence, after the rubbing is carried out on each of the alignment layers 11 and 21 of the first and second mother substrates 10 and 20, the first or second mother substrate 10 or 20 needs to be rotated by 180° for bonding.
FIG. 4 illustrates a block diagram of a related art rubbing apparatus for fabricating a liquid crystal display panel.
Referring to FIG. 4, the related art rubbing apparatus for fabricating a liquid crystal display panel includes first and second alignment layer forming units 1 and 2 for forming alignment layers on the corresponding surfaces of first and second mother substrates, first and second rubbing units 3 and 4 rubbing the alignment layers respectively formed on the surfaces of the first and second mother substrates, and a single body type turning buffer 8 receiving the first and second mother substrates from the first and second alignment layer forming units 1 and 2 through a first conveying unit 5 to transfer the mother substrates to the first and second rubbing units 3 and 4 through a second conveying unit 6 and receiving the first and second mother substrates rubbed by the first and second rubbing units 3 and 4 through the second conveying unit 6 to be sequentially rotated to be put into a cassette 7 through the first conveying unit 5.
FIG. 5 illustrates a perspective view of a single body type turning buffer according to the related art.
Referring to FIG. 5, the single body type turning buffer according to the related art includes a first support 32 having first tabs 31 regularly separated from one another to mount a first mother substrate thereon, a second support 42 having second tabs 41 regularly separated from one another to mount a second mother substrate thereon, and a turning unit 45 connected to the corresponding ends of the first and second supports 32 and 42 to rotate the first and second supports 32 and 42 at the same time.
The related art rubbing apparatus having a turning buffer for fabricating the liquid crystal display device is explained in detail with reference to FIGS. 4 and 5 as follows.
The first and second mother substrates having the alignment layers formed thereon by the first and second alignment layer forming units 1 and 2 are mounted on the corresponding first and second supports 32 and 42 of the single body type turning buffer 8 by the first conveying unit 5.
Subsequently, the first and second mother substrates mounted on the first and second supports 32 and 42 of the single body type turning buffer 8 are transferred to the first and second rubbing units 3 and 4 by the second conveying unit 6 to carry out the rubbing process thereon.
Then, the first and second mother substrates with the completed rubbing process by the first and second rubbing units 3 and 4 are mounted on the first and second supports 32 and 42 of the single body type turning buffer 8 by the second conveying unit 6, respectively.
Thereafter, the first and second mother substrates mounted on the first and second supports 32 and 42 of the single body type turning buffer 8 are simultaneously rotated by the turning unit 45 of the single body type turning buffer 8 and are then alternately transferred to the cassette 7 by the first conveying unit 5. Meanwhile, the cassette receiving the first and second mother substrates in the receiving space is transferred to other equipments carrying out a subsequent process.
As mentioned in the foregoing explanation, one of the rubbed first and second mother substrates should be rotated by 180° prior to bonding to the other rubbed mother substrate.
Hence, once the rubbed first and second mother substrates are mounted on the corresponding first and second supports 32 and 42 of the single body type turning buffer 8, the first and second supports 32 and 42 are rotated by 180°. One of the first and second mother substrates is then transferred to the cassette 7 through the first conveying unit 5. Subsequently, after the first and second supports 32 and 42 are rotated by 180° through the turning unit 45, the remaining mother substrate is transferred to the cassette 7 through the first conveying unit 5.
Thus, in the related art rubbing apparatus having the turning buffer for fabricating the liquid crystal display device including the single body type turning buffer, the first and second mother substrates are respectively transferred to the first and second rubbing units, and the rubbed first and second mother substrates are rotated at the same time to be alternately transferred to the cassette.
However, it takes a long time to transfer the rubbed first and second mother substrates to the cassette. Thus, a waiting time can be increased for the mother substrates to be transferred to the first and second rubbing units through the single body type turning buffer. Hence, productivity is reduced.